Numerical analysis of the effect on the combi boiler efficiency of heat exchanger different fin geometries used in the combi boilers

In this study, variations of the fin and tube of a plain-fin-tube heat exchanger with effects on the heat transfer and pressure drop were investigated. In the actual heat exchanger, two half fin between across the flue gas and tube were selected as a model. The temperature distribution, velocity distribution and pressure drop of the flue gas were studied. In the obtained models, variation of fin angles, the optimum distance of the fin spaces and the changing of (y) axis of the tube at the fin center to the effect of the heat transfer were investigated with different models. In the numerical calculations, the basic conservation equations in steady-state, three-dimensional (3-D) and laminar flow conditions were solved using a CFD computer code, the FLUENT and by GAMBIT software in the model drawing and meshed. Conjugate heat transfer both conduction and convection was analysed for all models. In the end of the numerical calculations, the maximum heat transfer has been found in the inclined fin angle ? = 30o, distance between fin space L z = 2,75 - 3 mm and tube axis value of c1 = 16 mm. Average Nusselt numbers were determined numerically for three different models and correlation equations vii were given analytically as functions of Reynolds and Prandtl numbers. Furthermore, the required additional energy value due to pressure drop has been determined too small according to gain heat transfer value. In this study, the obtained results have been seen in a good agreement with the results in the literature.